Button hole attachment for zigzag sewing machines

ABSTRACT

A buttonhole attachment for a zigzag sewing machine having a laterally oscillating needle bar includes a lever means angularly reciprocated by a pin on the needle bar during the longitudinal stitching movement, and operating a ratchet wheel by means of a pawl. A rack member with an oblong endless inner gear engaged by a pinion turning with the ratchet wheel is connected with the presser foot so that the same moves along an oblong endless path corresponding to the outline of a buttonhole, and moves the fabric accordingly so that the laterally oscillating needle stitches a buttonhole.

nited States Hanyu Jan. 1, 11974 [54] BUTTON HOLE ATTACHMENT FOR 2,300,921 11/1942 Hinman 112 77 Z Z G SE MACHINES 3,051,106 8/1962 Caldwell et al..,...

2,804,035 8/1957 Baehr et a1. 112/77 Inventor: Susumu Hanyu, Tokyo, Japan ,llanome Sewing Machine (10., Ltd, Tokyo, Japan Filed: Nov. 4, 1968 Appl. No.: 773,198

Assignee:

Foreign Application Priority Data Nov. 6, 1967 Japan 42/93245 Nov. 10, l967 Japan 42/94386 Primary Examinerl-l. Hampton Hunter Att0rney-Michael S. Striker [57] ABSTRACT A buttonhole attachment for a zigzag sewing machine having a laterally oscillating needle bar includes a lever means angularly reciprocated by a pin on the needle bar during the longitudinal stitching movement, and operating a ratchet wheel by means of a pawl. A rack member with an oblong endless inner gear engaged by a pinion turning with the ratchet wheel is connected with the presser foot so that the same moves along an oblong endless path corresponding to the outline of a buttonhole, and moves the fabric accordingly so that the laterally oscillating needle stitches a buttonhole.

10 Claims, 7 Drawing Figures PATENTEDJAN H 3.182.307.

sum 1 or 2 FTE 6 BUTTON HOLE ATTACHMENT FOR ZIGZAG SIEWTNG MACT-IIIINES DETAILED EXPLANATION OF Til-IE INVENTION The present invention relates to an improvement of button hole attachment for a zigzag sewing machine which is fitted to a zigzag sewing machine and is moved conjointly with the amplitude motion of needle-bar and with the selected use of a suitable cam enabling to obtain a desired button hole cross-stitches. Moreover due to a proper structure of the attachment replacement of the cam can be easily performed so that a smooth button hole stitching operation is provided.

It is well known to fit a buttom hole attachment to a zigzag machine to actuate it with the upward and downward motion of a needle-bar of the sewing machine. However, in this kind of attachment, it is not always easy to execute replacement of the cam. The cam thus fitted'cannot be stable, which is one of the deficiencies of the conventional device. In these circumstances, even if such button hole attachment is adopted button hole stitching operation is not correctly performed, which is another disadvantage of the conventional one.

The present invention is so designed as to eliminate the above mentioned deficiencies of the conventional button hole attachment. That is, the fundamental object of this invention is to obtain always a correct and exact button hole stitching. For this purpose in this invention a rotatable member and cam retaining member are provided. The rotatable member is integrally composed of a ratchet, a gear engaging the inner gear teeth of a cam piece, and a shaft which is engaged by a guide groove of the cam piece. Cam retaining member elastically engages with and disebgages from the fitting portion of a sliding member into which the cam piece is fitted. that is, with such a provision, the rotating motion of rotatory member becomes very smooth and exact, moreover the cam piece for transferring the sliding member can be appropriately and easily replaced. and also the cam piece is secarely fitted in the sliding member. The sliding movement of sliding member caused by the smoothly operating rotary member through thus stabilized can piece makes it possible to make a constant and exact button hole stitching. In this invention the bottom surface of a cloth presser member mounted on the sliding member are provided with small projections respectively inclined to the outer sides with respect to the intersected lines. With these projections when needle piercing into the cloth moves upward, there is no fear that the cloth is drawn up with the needle from the needle drop hole of the throat plate of the sewing machine, because a tention is usually applied to the cloth by these projections so that the button hole stitching is regularly performed by means of a guide operation of cam piece. In this respect too, this invention insures the exact button hole stitching.

Another object of this invention is to provide a button hole attachment, in which the cam piece can be easily replaced. For this purpose, in this invention, the cam piece is so formed as to be fitted into the sliding member at the correct fixed position relative to the same, and at the same time the cam piece is elastically retained against the bottom surface of the sliding member by means of a cam retaining member snappingly engagable with and disengageable from an edge of the sliding member. This cam retaining member prevents the cam piece from slipping-out of the sliding member and maintains cam member in the sliding member. The cam retaining member is easily detachable from the edge of sliding member, whereby replacement of cam becomes very easy.

Another object of this invention is to positively actuate the retaining motion of the rotary member which engages the cam piece installed in the sliding member and is to slidingly move the sliding member in accordance with the movement of the cam piece. A feeding member and a ratchet are provided in combination. The feeding member is spring biased to engage the ratchet and is formed with a nail portion and a guide portion at one end thereof. The ratchet is provided on the rotary member so that it may be engaged by the nail of feeding member, and also a guide channel is provided on the rotary member in concentrical relation with the ratchet to receive the guide portion. With such an arrangement, the guide portion of the feeding member is at all times guided by the guide channel so that the nail portion may be at all times maintained in a correct engaging position with respect to the ratchet while it rotates the rotary member. This rotary member is positively and exactly rotated by the feeding member.

The concrete structure and characteristics of this invention will be more clearly understood from the following description of the preferred embodiment of this invention in reference to the drawings, in which;

FIG. 1 is an oblique view of the preferred embodiment of this invention with a cover being shown by an imaginary line;

FIG. 2 is an exploded oblique view of the embodiment in FIG. 1;

FIG. 3 is an oblique view of a rotary member as seen from the bottom side of the same member composing part of this invention;

FIG. 41 is an oblique view of the cam piece composing part of this invention;

FIG. 5 is an oblique view of a cloth presser member as seen from the bottom side of the same comprising also part of this invention;

FIG. 6 is a transverse sectional view of the cloth presser member in FIG. 5; and,

FIG. 7 is a front elevational view of rotary member and cam piece, with some parts in section, as they are assembled.

Now a concrete and detailed explanation will be given with reference to the drawings. The button hole attachment, the embodiment of this invention is as explodedly shown in FIG. 2 mainly composed of base plate 11, sliding plate 2, rotary member 3, retaining plate 4, rack member or cam piece 5, feeding bar 6, brake 7, lever 8 and cover 9. The base plate T is at its intermediate portion bent to form a step 119. On one side of the step 119 and at one side of the base plate, the base plate 1 is bent to form upstanding portions E3 E3. The upstanding portion ]13 is higher than the portion T3, and has a transverse bent projection T2 by which the button hole attachment is attached to the presser bar 1110 of the sewing machine as illustrated in lFllG. ll. At the intermediate part of the upstanding portion 13 there is provided a hole 14 at which the lever is tumably mounted. The upstanding portion ll3' has a lug 116 bent out therefrom to serve as a stopper for an arm 841 of the lever Further the upstanding portion R3 has a hole 69 adjacient to the step 19, into which one end of spring 67 is secured. The other side away from the step 19, the base plate ll has at its end part a bearing hole with a flange, into which the shaft portion of the rotary member is fitted for rotation. Between the hole 10 and the step 19 are provided holes 17 18 into which screws 96 96 pass to secure the cover 93, and also holes 76 76 into which screws 75 75 pass to secure the brake 7 on to the base plate. Moreover, on the aforementioned one side of said step 19 the base plate 1 has a hole by which the sliding plate 2 of a feeding means 2, 24 is slidably mounted on the base plate by means of stepped screw 100 passing through an elongated slot 22 of the sliding plate 2 and the hole 15 from the underside of the sliding plate 2 and tightly screwed by nut 101 on the upper surface of the base plate 1.

Sliding plate 2 is provided with the elongated slot 22 in the middle portion thereof, and on its side, a step 2a is formed which is almost the same level as the step 19 of the base plate 1. The sliding plate 2 projects at its one end to form forked supports 23 23 and between the supports 23 23 is fitted a cloth presser 24 at its intermediate portions by means of pivots 29 29 oppositely provided on the supportax 29 29. One of the supports 23 is at its free end bent upward and further bent horizontally to form a stopper 25 which engages the upper surface of the presser 24 and restricts the angular range of the presser foot 24. The cloth presser foot 24 has at its middle portion a rectangular slot 26 through which the needle of the machine reciprocates longitudinally for stitching and laterally for a zigzag movement, and endwise as well as sidewise of the slot 26 then are positively provided indicating marks 28 28 which indicate the starting position and stitching direction of the buttom hole seams. Moreover, on the bottom of the presser 24, as shown in FIG. 5 there are porvided a plurality of small projections 27 which are all arranged to be inclined to the outer sides from the center so as to apply a tension to the cloth pressed by the presser. The sliding plate 2 is at the other end portion oppositely formed with enlarged U-shaped guide brackets 2 2 and an opening 20 between the frames in which the cam piece 5 is fitted. The opening is elongated and oppositely formed with notches 20 20', and also oppositely formed with recesses 20" 20" on both sides thereof for convenient replacement of the cam piece 5.

As it is evident with reference to FIGS. 2 and 3 the rotary member 3 is provided with a thumb shaft 30 in the center of its upper surface, and it also around the thumb shaft 30 and each concentrically provided with a ring-sahped rib 3, a guide groove 32 on the outer side of the rib 33 and a ratchet 31 on the outer side of the guide groove 32 and on the outer periphery of the rotary member. On the bottom of the rotary member 3 are arranged a flange 37, a stepped seat 38 a small gear 35 and a guide pin 36 which are all concentrical with the thumb shaft 30. Such a rotary member 3 may be integrally made of synthetic resin as mentioned above. As specifically illustrated in FIG. 2 and FIG. 7, the rotary member 3 is installed in the bearing hole 10 of the base plate 1 and rotatably carried there with the help of a C- shaped washer 102 which is attached to the stepped seat 38 of the rotary member on the bottom side of the base plate 1 to securely hold the rotary member therein. With the rotary member 3 thus installed, the gear 35 is adapted to engage the gear teeth 51 of the rack member or cam piece 5 which is fitted into the opening 20 of the sliding member 2. The cam piece 5 is almost elliptical, and around the lower periphery of the body there is provided a flange 52 with oppositely arranged projections 50 50 thereon. On the body 50 of this cam piece, there is formed an elongated slot which is provided with gear teeth 51 therearound forming an oblong inner gear engaged by the gear 35 of the rotary member 3. At the bottom of this geared slot 51, there is provided an elongated endless groove 53 which is adapted to receive the guide pin 36 of the gear 35 and cooperate with it in guiding the movement of gear piece 5, which is securely fitted in the opening 20 of the sliding plate 2 with the flang 52 contacted against the bottom surface of the sliding plate 2 and the projections 50 50' being in a fitted engagement with the corresponding notches 20' 20 of the opening 20 of the plate 2. A desired numbers of cam pieces or rack members 5 may be obtained by molding them out in accordance with the desired shapes and dimensions of buttom holes to be stitched for replacement of the same. To fixedly maintain the cam piece 5 in the opening 20 of the sliding plate 2 as mentioned above, a cam retaining plate 4 is provided. This is a plate made of appropriate elastic material and on one end thereof, are oppositely arranged pivot-supports 41 41. By the supports 41 41, the elastic plate 4 is pivotally supported on support protrusions 21 21 which are oppositely formed on both sides of the sliding plate 2 between the step 2a and the U-shaped frames 2' 2'. The retaining plate 4 is at the other end bent out to form an engaging portion 42 so that it is elastically snapped into or out of engagement with the edge 2b of sliding plate 2. Also close to the other end of this plate 4 there is provided an elongated hole 43 through which to insure a distinctive mark of cam piece 5 shown on the bottom thereof while it is in use.

The aforementioned hole 14 in the middle of the upstanding portion 13 of base plate 1, as mentioned above, is superposed with hole 83, of an actuating lever 8, and stud is inserted into these holes to tumably mount the lever 8 on the upstanding portion 13. The lever 8 is prevented from laterally moving with respect to the outstanding portion 13 by means of a flange 85' of the stud 85. On the stud 85 protruded out of the holes 14 83, a coil spring 87 is mounted. The spring 87 is at its one end 89 secured in a notch 86 formed on the outer end of the stud 85, and is at the other end 88 detained on a shoulder 8a of the lever 8. In this state the arm 81 of lever 8 extends to the needle bar 111 of the sewing machine, and the arm 84 extends to the opposite direction, when the attachement is attached to the presser bar of sewing machine as illustrated in FIG. 1. An engaging portion of arm 81 of lever 8 is made to contact pin 112 projecting sidewave from needle bar 1 1. By up and down reciprocating motion of the needle bar 1 11, the actuating lever 8 is angularly reciprocated around the pivot stud 85. The downward turning movement of the lever 8 is restricted, as mentioned above, by the aforementioned stopper lug 16 which is adapted to engage the arm 84 of lever 8.

In the upper position spaced from the pivot hole 83 of lever 8 is provided another pivot hole 82. The pivot hole 82 is superposed with pivot hole 61 which is formed at one end of feeding bar 6 and the lever 8 and feeding bar 6 are connected by a stud 66 passing through the holes 82 61. The feeding bar 6 is folded transversely in the middle thereof to form a flat extention 65 as shown in FIGS. 1 and 2. The flat extention 65 of feeding bar 6 is disposed almost in parallel with the flat surface of base plate 1, and is forked at its forward end to form a guide portion 63 and an actuating portion 62. As illustrated the guide portion 63 is adpated to engage the circular guide groove 32 of rotary member 3 and the actuating portion 62 is a pawl adapted to engage the ratchet 31 of rotary member 3, so that the bar 6 may positively and accurately rotate the rotary member 3. Moreover, the feeding bar 6 is provided a hole 66 at a position spaced from the hole 61. A coil spring 67 is at one end attached to the hole 68 and at the other end secured to the aforementioned hole 69 formed in the lower upstanding portion 13' of base plate 1, and keeps the fedding bar 6 in contact engagement with the rotary member 3 as described above.

Brake 7 consists of folded-upstanding part 7ll, seat 70 disposed at right angles with the upstanding part 71 and an extension part 72 which is associated with the upstanding part 71 and at the free end formed with an engaging portion 73. The brake 7 is fixed on the base plate 1 by means of a pair of screws 75 75 which are respectively screwed into the superposed screw holes 74 74 and 76 76 respectively formed on the brake 7 and the base plate as illustrated in FIG. 2. The engaging portion 73 of brake 7 is adapted to elastically engage the outer circumference of ratchet 31 to work as a brake.

As illustrated in FIG. 1 in imaginary lines, a cover member 9 is provided to cover the main portion of this buttom hole attachment. In reference to FIG. 2, the cover 9 is all surrounded with a depending wall 95. However the wall is at one end of the cover formed with a recess 92 to allow a part of the feeding bar 6 to project therefrom, and also the wall is at the other end of the cover reduced a little to allow the edge 26 of sliding plate 2 to project therefrom, for the edge 26 of the sliding member 2 is snappinly arrested by the engaging part 42 of carn retaining plate 4. The cover member 9 has also a hole 9i in the other end portion thereof and through which hole 911 in the thumb shaft 36 of rotary member 3 porjects out in order to be accessible. Beside and along the hole 91 there is provided an arrow shaped indication 94 to indicate the direction of manual rotating operation of the thumb shaft 36 when it becomes necessary. ln the inner side of said cover 9 are equipped a pair of depending struts 9'7 96 which are respectively hollow and threaded inside thereof. The cover 9 is secured to the base plate 1 by the means of a pair of screws 96 96 passing through the respective holes l7 18 in the base plate ll from the bottom of base plate 1 and respectivelly screwed into the struts 97 96.

To describe the operation of the according to this invention: As shown in PEG. 1, by securing the U-shaped bent projection 12 of base plate l to the presser bar llltl of sewing machine, the attachment is fixedly mounted on the sewing machine, and the arm M of actuating lever g is in contacting engagement with the pin llll2 transversely fixed on the needle bar ill by the action of spring 67. When the machine is driven in this connection, lever 6 is angularly actuated around to stud 85 against and by the action of spring 37 by up and down reciprocating stitch movement of the needle bar Hill, and in affect feeding bar 6 is longitudinally reciprocated, so that pawl portion 62 at the free end of the feeding bar 6 turns the ratchet 311 step by step while the guiding portion 63 is in fitted engagement with the guide groove 32 which is disposed adjacent to the ratchet 91. Thus, the rotatory member 3 is rotated step by step, and with this the small gear 36 is rotated to shift the cam piece 5. Consequently the sliding plate 2 secured to rack member or cam piece 5 is made to slidingly shift along an endless oblong path in accordance with the oblong endless inner gear 51 and with the oblong endless guide groove 53 of cam piece 5. As the sliding plate 2 is connected to base plate i with its elongated hole 22 and embraces the side edges of base plate 1 with its U-shaped frames 2 2', the sliding member 2 is correctly shifted. Consequently, it is evident that needle H3 which drops into needle hole 26 of cloth presser 24 zigzag stitches a correct and exact button hole which is controlled by a selected cam peice 5, since the cloth pressed by the presser foot 24; against the machine table is correctly shifted together with the sliding plate 2 along an endless oblong path. Cam piece 5 fitted in the opening 26 of the sliding plate 2 is easily removed and replaced by snappingly unlocking the cam retaining plate 4 from the edge 26 of slide plate 2. U-shaped brackets 2' permit displacement of plate 2 to a position in which pinion 35 is disengagedfrom inner gear 51 for exchange. It will be seen that means 3 5 form a transmission for transforming the reciprocating motion of actuating portion 62 into a movement of presser foot 24 along an oblong endless path.

I claim:

ll. Buttonhole attachement for a zigzag sewing machine including a presser bar, and a needle bar with a needle longitudinally reciprocating in a stitching movement and transversely oscillating in a zigzag movement, comprising a base detachably mounted on said presser bar; actuating means movable mounted on said base and having an engaging portion and an actuating portion, said engaging portion engaging said needle bar so that said actuating portion is reciprocated by said longitudinal stitching movement of said needle bar; feeding means movable mounted on said base and including a presser foot having a bottom face for engaging a fabric; and transmission means connecting said reciprocating actuating portion with said feeding means for transforming said reciprocating movement of said actuating portion into movement of said presser foot along an oblong endless path corresponding to the outline of a buttonhole whereby the fabric under said presser foot is moved without oscillation along said endless path while zigzag buttonhole stitching is made by said transversely oscillating and longitudinally reciprocating needle in the fabric moving along said oblong endless path.

2. Buttonhole attachment attachment as claimed in claim 1 wherein said actuating means include a projection on said needle bar, lever means pivotally mounted on said feeding means and incuding one arm with said engaging portion, and an other arm with said actuating portion, and a spring means biassing said lever to a position in which said engaging portion abuts said projection on said needle bar and is angularly reciprocated by the same.

3. Buttom hole attachemnt as claimed in claim 2 wherein said transmission includes a ratchet wheel; and wherein said actuating portion of said other arm includes a ratchet pawl reciprocating with said lever means during longitudinal reciprocation of said needle bar, and engaging said ratchet wheel for stepwide rotating the same in one direction and thereby stepwise moving said pressor foot along said oblong endless path.

4. Buttonhole attachment as claimed in claim 1 wherein said transmission means includes a rotary member mounted on said base for rotation and having ratchet teeth arranged in a circle and a circular guide groove concentric with said circle; wherein said actuating portion includes a guide part engaging said guide groove and a pawl part cooperating with said ratchet teeth for stepwise rotating said rotary member in one direction; and wherein said transmission means include motion transmitting means connecting said rotary member with said presser foot for transforming the rotary movement of said rotary member into movement of said presser foot along said oblong endless path.

5. Buttonhole attachment as claimed in claim 4 wherein said motion transmitting means include a pinion and a guide pin secured to said rotary member for rotation, and a rack member detachably and exchangeably secured to said feeding means, and formed with a slot having an inner gear and an oblong endless guide grooove parallel to said inner gear and having the shape of said oblong endless path; and wherein said pinion meshes with said inner gear and said guide pin slides in said guide grooves so that said rack member and thereby said feeding means and said presser foot move along said oblong endless path.

6. Buttonhole attachement as claimed in claim 5 wherein said feding means includes a sliding plate mounted on said base and supporting said presser foot, said sliding plate having an opening matching the contour of said rack member; wherein said rack member is detachably located in said opening; and wherein said feeding means incudes a retaining plate mounted on said sliding plate and having arresting means for engaging said sliding plate and said rack meber for retaining the same in said opening.

7. Buttonhole attachment as claimed in claim 6 wherein said button face of said presser foot has pyramid shaped projections for stretching said fabric.

8. Button hole attachment as claimed in claim 6 wherein said base includes a base plate; wherein said sliding plate is slidingly mounted on said base plate and has U-shaped guide brackets on opposite sides of said sliding plate for limiting transverse movement of the same to a predetermined distance to a position in which said pinion is disengaged from said inner gear so that said rack member can be detached from said opening and replaced.

9. Buttonhole attachment as claimed in claim 4 comprising a brake member fixedly secured to said base and having a resilient arm slidingly engaging the periphery of said rotary member.

10. Buttonhole attachemnt for a zigzag sewing machine having a presser bar and a needle bar with a needle, compising a base plate mounted on said preer bar of the sewing machine, a sliding plate slideably mounted on said base plate, a presser foot pivotally mounted at one end of said sliding plate, a rack member detachably mounted on said sliding plate and formed with a geared slot and with an elongated endless groove, a rotary member rotatably mounted on said base plate and including a ratchet, a circular guide groove concentric with said ratchet, a thumb shaft within said circular guide groove, a pinion disposed to engage said geared slot, and a guide pin for engaging said elongated endless groove of said rack member; a lever operatively connected to said needle bar of the machine and actuated by the longitudinal reciprocation of the same, a feeding bar connected at one end to said lever, and having another end with a guide part for engaging said circular groove of said rotary member, and an actuating pawl part for engaging said ratchet; and a retaining plate mounted on said sliding plate and adapted to retain said rack member on said sliding plate, said retaining plate having at one end an elastic engaging part so that said retaining plate may snap into and out of engagement with said sliding plate. 

1. Buttonhole attachment for a zigzag sewing machine including a presser bar, and a needle bar with a needle longitudinally reciprocating in a stitching movement and transversely oscillating in a zigzag movement, comprising a base detachably mounted on said presser bar; actuating means movable mounted on said base and having an engaging portion and an actuating portion, said engaging portion engaging said needle bar so that said actuating portion is reciprocated by said longitudinal stitching movement of said needle bar; feeding means movable mounted on said base and including a presser foot having a bottom face for engaging a fabric; and transmission means connecting said reciprocating actuating portion with said feeding means for transforming said reciprocating movement of said actuating portion into movement of said presser foot along an oblong endless path corresponding to the outline of a buttonhole whereby the fabric under said presser foot is moved without oscillation along said endless path while zigzag buttonhole stitching is made by said transversely oscillating and longitudinally reciprocating needle in the fabric moving along said oblong endless path.
 2. Buttonhole attachment attachment as claimed in claim 1 wherein said actuating means include a projection on said needle bar, lever means pivotally mounted on said feeding means and including one arm with said engaging portion, and an other arm with said actuating portion, and a spring means biassing said lever to a position in which said engaging portion abuts said projection on said needle bar and is angularly reciprocated by the same.
 3. Button hole attachment as claimed in claim 2 wherein said transmission includes a ratchet wheel; and wherein said actuating portion of said other arm includes a ratchet pawl reciprocating with said lever means during longitudinal reciprocation of said needle bar, and engaging said ratchet wheel for stepwise rotating the same in one direction and thereby stepwise moving said presser foot along said oblong endless path.
 4. Buttonhole attachment as claimed in claim 1 wherein said transmission means includes a rotary member mounted on said base for rotation and having ratchet teeth arranged in a circle and a circular guide groove concentric with said circle; wherein said actuating portion includes a guide part engaging said guide groove and a pawl part cooperating with said ratchet teeth for stepwise rotating said rotary member in one direction; and wherein said transmission means include motion transmitting means connecting said rotary member with said presser foot for transforming the rotary movement of said rotary member into movement of said presser foot along said oblong endless path.
 5. Buttonhole attachment as claimed in claim 4 wherein said motion transmitting means include a pinion and a guide pin secured to said rotary member for rotation, and a rack member detachably and exchangeably secured to said feeding means, and formed with a slot having an inner gear and an oblong endless guide groove parallel to said inner gear and having the shape of said oblong endless path; and wherein said pinion meshes with said inner gear and said guide pin slides in said guide groove so that said rack member and thereby said feeding means and said presser foot move along said oblong endless path.
 6. Buttonhole attachment as claimed in claim 5 wherein said feeding means includes a sliding plate mounted on said base and supporting said presser foot, said sliding plate having an opening matching the contour of said rack member; wherein said rack member is detachably located in said opening; and wherein said feeding means includes a retaining plate mounted on said sliding plate and having arresting means for engaging said sliding plate and said rack member for retaining the same in said opening.
 7. Buttonhole attachment as claimed in claim 6 wherein Said button face of said presser foot has pyramid shaped projections for stretching said fabric.
 8. Buttonhole attachment as claimed in claim 6 wherein said base includes a base plate; wherein said sliding plate is slidingly mounted on said base plate and has U-shaped guide brackets on opposite sides of said sliding plate for limiting transverse movement of the same to a predetermined distance to a position in which said pinion is disengaged from said inner gear so that said rack member can be detached from said opening and replaced.
 9. Buttonhole attachment as claimed in claim 4 comprising a brake member fixedly secured to said base and having a resilient arm slidingly engaging the periphery of said rotary member.
 10. Buttonhole attachment for a zigzag sewing machine having a presser bar and a needle bar with a needle, comprising a base plate mounted on said presser bar of the sewing machine, a sliding plate slidably mounted on said base plate, a presser foot pivotally mounted at one end of said sliding plate, a rack member detachably mounted on said sliding plate and formed with a geared slot and with an elongated endless groove, a rotary member rotatably mounted on said base plate and including a ratchet, a circular guide groove concentric with said ratchet, a thumb shaft within said circular guide groove, a pinion disposed to engage said geared slot, and a guide pin for engaging said elongated endless groove of said rack member; a lever operatively connected to said needle bar of the machine and actuated by the longitudinal reciprocation of the same, a feeding bar connected at one end to said lever, and having another end with a guide part for engaging said circular groove of said rotary member, and an actuating pawl part for engaging said ratchet; and a retaining plate mounted on said sliding plate and adapted to retain said rack member on said sliding plate, said retaining plate having at one end an elastic engaging part so that said retaining plate may snap into and out of engagement with said sliding plate. 